Using electrical and/or electronic components generates heat, which needs to be dissipated in order to prevent the component from overheating and thus to prevent failure of the component.
Using, inter alia, PCMs (latent heat storage materials) to dissipate heat is known, since said materials can both store heat in the form of latent heat and release it again. PCMs are subject to a phase transition when heat is supplied or released. This can for example be a transition from the solid phase into the liquid phase, or vice versa. When heat is supplied to or dissipated from the PCM, when the phase transition point is reached, the temperature remains constant until the material is completely changed. The heat supplied or dissipated during the phase transition which does not cause the material to change temperature is referred to as latent heat.
Possible phase-change materials are, for example, paraffins, waxes, sugar alcohols, alcohols, sugars, polymers, in particular thermoplastic polymers, water, organic acids such as fatty acids, aqueous salt solutions such as salt hydrates, or amides (WO2008087032A1, U.S. Pat. No. 8,580,171B2).
Owing to the fact that the thermal conductivity of most PCMs is rather low, in the range of from 0.3 to 0.4 W/(m·K), the process of heat absorption or heat emission is very slow and thus not industrially relevant in most cases.
The problem of the process of heat absorption or heat release when using PCMs being very slow can be overcome by using a latent heat storage composite material, the PCM being combined with an auxiliary component having high thermal conductivity, such as graphite, in particular expanded graphite. Expanded graphite is particularly well suited as an auxiliary component owing to the high thermal conductivity and additionally has good chemical resistance (U.S. Pat. No. 8,580,171B2, WO2008087032A1).
In order to use a latent heat storage composite material, the PCM must be prevented from leaking out during the transition into the liquid phase. Encapsulating PCM is known. A drawback of this is the difficulty of encapsulating the PCM. This is mainly caused by the PCM undergoing a change in volume of up to 15% during the phase change, thus resulting in a change in dimension in the composite material produced therefrom of more than 5%, as a result of which the encapsulation fails after just a short period of use, on account of the fatigue of the capsule material. DE102013215255A1 overcomes the difficulty of encapsulating a PCM by using an elastomeric matrix. In this case, the PCM is embedded in an elastomeric matrix. However, this results in additional drawbacks. The elastomeric matrix also has a low thermal conductivity and, in addition, no dimensionally stable components can be formed by means of said materials, since the entire complex becomes soft when the compound is melted.
The known PCM/graphite composite materials have the drawback that a relatively high (at least >10 wt. %) binder proportion needs to be used since otherwise the composite material does not have integrity. For a high binder proportion, conductive additive mixtures of at least 20 wt. % need to be admixed, as a result of which the storage capacity is reduced proportionally, but by at least 25%.